Using Rhom in JavaScript

The RhoMobile Suite provides several methods of handling device data. For RhoMobile Suite 5.3 and higher is the ORM common API, which supports JavaScript and Ruby. RMS 5.2 and lower support the original Rhom API (for Ruby) and the ORM API documented here, which adds JavaScript support to Rhom via the OPAL library.

• Creating a JavaScript Model
• Adding new items
• Retrieving objects
• Counting objects
• Updating
• Deleting
• Transactions
• Executing SQL
• Resetting database
• Related reading

Creating a JavaScript Model

The first step in using Rhom is to create a model class with the required attributes. Models are created in JavaScript using the ORM.addModel method, which defines a class reference for the model and makes it available to the application.

When your application pages load, execute the Rho.ORM.addModel function for every model defined in the application.

// Models MUST be defined when your HTML pages load

// Either set a global reference... 
var userModel = Rho.ORM.addModel(function(model) {
    model.modelName('User');
    model.property('name','string');
    model.property('email','string');
    // optionally enable sync for rhoconnect applications:
    // model.enable('sync');
    // optionally define model as fixedSchema (default is propertyBag):
    // model.enable('fixedSchema');
});

// ...or define the model without a global reference
Rho.ORM.addModel(function(model) {
    model.modelName('Product');
    model.property('name','string');
    model.property('qty','string');
});

Once created, models can be retrieved using the ORM.getModel method:

var productModel = Rho.ORM.getModel('Product');

Adding new items

The fastest way to insert a single item into the database is to use the create method to create a new model object and save it to the database:

var user = userModel.create({
            name: 'Alice', 
            email: 'alice@example.com'});

You also can create a new model object without saving it automatically, and then explicitly use the save method. This is useful for updating some of the object attributes before saving:

var user = userModel.make({name: 'Alice'});
// update the object
user.email = 'alice@example.com';
user.save();

Retrieving objects

Use the find method to retrieve all objects for a model or only those matching given conditions:

Getting all objects for a model

var users = userModel.find('all');

Finding objects matching conditions

var users = userModel.find(
                'all', 
                {
                    conditions: {name: 'Alice'}
                }
            );

Ordering the objects

Use the order and orderdir parameters to retrieve objects sorted by one or more attributes:

// order by one attribute
var users = userModel.find(
                'all', 
                {
                    order: 'name', 
                    orderdir: 'DESC', 
                    conditions: {...} // JavaScript API requires conditions
                }
            );

// order by multiple attributes
var users = userModel.find(
                'all', 
                {
                    order: ['name', 'email'], 
                    orderdir: ['ASC', 'DESC'], 
                    conditions: {...} // JavaScript API requires conditions
                }
            );

Sorting also can be done with a user-defined function:

// order by one attribute
var users = userModel.find(
    'all',
    {
        orderFunction: function(a, b) { return a <= b }
    }
); 

// order by multiple attributes
var users = userModel.find(
    'all',
    {
        orderFunction: function(a, b) {
                return a.name <= b.name && a.email <= b.email
            }
    }
);

Retrieving specific attributes

If only some attributes in an object are needed for a particular action, increase app performance by using the select parameter to choose only the required attributes:

JavaScript syntax: :::javascript var users = userModel.find( ‘all’, { select: [‘name’], conditions: {…} // JavaScript API requires conditions } );

Retrieving only the first object matching conditions

Use the first method (instead of all) when calling find to get only the first object matching the given condition(s):

var user = userModel.find(
                'first', 
                {
                    conditions: {name: 'Alice'}
                }
            );

Counting objects

Use the count parameter with find method to get a count of objects matching given condition(s):

JavaScript syntax: :::javascript var count = userModel.find( ‘count’, { conditions: {name: ‘Alice’} } );

Updating

The fastest way to add or update object attributes is to save to the database using the update_attributes method:

JavaScript syntax: :::javascript var user = userModel.find(‘first’, {conditions: {name: ‘Alice’}); user.updateAttributes({ name: ‘Bob’, email: ‘bob@example.com’});

Deleting

Delete one object

To delete one model object, use the destroy method on the object to be deleted:

JavaScript syntax: :::javascript var user = userModel.find(‘first’); user.destroy();

Delete multiple objects

Use the deleteAll method to delete all objects for a model or only those matching given condition(s):

JavaScript syntax: :::javascript // delete all objects userModel.deleteAll();

// delete only objects matching :conditions
userModel.deleteAll({conditions: {name: 'Alice'}})

Transactions

For database operations that must either succeed or fail as a group without leaving any partially completed operations, use transactions to group them together. Combine any set of object/model operations, such as ‘insert/update/delete’ under a transaction:

// open 'app' partition
var db = new Rho.Database(Rho.Application.databaseFilePath('app'),'app');
db.startTransaction();
try
{
    // do multiple operations
    db.executeSql("update User set name=?, email=? where object=?",["Alice","alice@example.com","12345"]);
    db.executeSql("update User set name=?, email=? where object=?",["Bob","bob@example.com","67890"]);

    // no errors, so commit all the changes
    db.commitTransaction();
}
catch
{
    // on error rollback all changes
    db.rollbackTransaction();
}
finally // always close every database connection you open
{
    db.close();
}

Executing SQL

Use the Database.executeSql method to execute SQL statements directly on the database:

JavaScript syntax: :::javascript try {

var db = new Rho.Database(Rho.Application.databaseFilePath('app'),'app');
var result = db.executeSql('SELECT * FROM User');  // result is an array of hashes, where each hash is a record
} finally {
    db.close();
}

Use the Database.executeBatchSql to execute a series of SQL statements in a single method call:

db.executeBatchSql("UPDATE User set valid=0; Update Account set active=0");

Resetting database

To recover the database from a bad or corrupt state or if the RhoConnect server returns errors, use the following method to delete all objects for given model(s):

JavaScript syntax: :::javascript Rho.ORM.databaseFullResetEx({‘models’: [‘User’], ‘reset_client_info’: true, ‘reset_local_models’: true});

Related reading

• Database API reference
• ORM API reference
• ORMModel API reference